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Substrate (chemistry)

About: Substrate (chemistry) is a research topic. Over the lifetime, 35902 publications have been published within this topic receiving 740722 citations. The topic is also known as: enzyme substrate.


Papers
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Journal ArticleDOI
TL;DR: The structure of a truncated form of the γ‐subunit of phosphorylase kinase (PHKγt) has been solved in a ternary complex with a non‐hydrolysable ATP analogue and a heptapeptide substrate related to both the natural substrate and to the optimal peptide substrate.
Abstract: The structure of a truncated form of the gamma-subunit of phosphorylase kinase (PHKgammat) has been solved in a ternary complex with a non-hydrolysable ATP analogue (adenylyl imidodiphosphate, AMPPNP) and a heptapeptide substrate related in sequence to both the natural substrate and to the optimal peptide substrate. Kinetic characterization of the phosphotransfer reaction confirms the peptide to be a good substrate, and the structure allows identification of key features responsible for its high affinity. Unexpectedly, the substrate peptide forms a short anti-parallel beta-sheet with the kinase activation segment, the region which in other kinases plays an important role in regulation of enzyme activity. This anchoring of the main chain of the substrate peptide at a fixed distance from the gamma-phosphate of ATP explains the selectivity of PHK for serine/threonine over tyrosine as a substrate. The catalytic core of PHK exists as a dimer in crystals of the ternary complex, and the relevance of this phenomenon to its in vivo recognition of dimeric glycogen phosphorylase b is considered.

187 citations

Journal ArticleDOI
TL;DR: A potato lipoxygenase (EC 1.13) was found to have a pH optimum at 5.5-6.0 and was inactive at pH 9.0 as discussed by the authors.
Abstract: A lipoxygenase (EC 1.13.1.13) was partially purified from potato tubers and was shown to differ from previously characterized soya-bean lipoxygenases in the positional specificity and pH characteristics of the oxygenation reaction. The potato enzyme converted linoleic acid almost exclusively (95%) into 9-d-hydroperoxyoctadeca-trans-10,cis-12-dienoic acid. The 13-hydroperoxy isomer was only a minor product (5%). Linolenic acid was an equally effective substrate, which was also oxygenated specifically at the 9-position. The enzyme had a pH optimum at 5.5–6.0 and was inactive at pH9.0. A half-maximal velocity was obtained at a linoleic acid concentration of 0.1mm. No inhibition was observed with EDTA (1mm) and cyanide (1mm) or with p-chloromercuribenzoate (0.2mm). Haemoproteins were not involved in the lipoxygenase activity. The molecular weight of the enzyme was estimated from gel filtration to be approx. 105. Preliminary evidence suggested that the enzyme oxygenated the n–10 position of fatty acids containing a penta(n–3, n–6)diene structure.

187 citations

Patent
12 Jul 1996
TL;DR: In this article, a sensor for measuring a concentration of an analyte in a solution is described, which comprises a substrate layer, an electrode layer and an immobilized enzyme layer.
Abstract: A sensor for measuring a concentration of an analyte in a solution. The sensor comprises a substrate layer, an electrode layer and an immobilized enzyme layer. The sensor further includes an enzyme/polymer layer and/or a hydrophobic layer. The enzyme/polymer layer includes an enzyme disposed within a polymer matrix. The hydrophobic layer is formed from a material that is more hydrophobic than the immobilized enzyme layer material. In certain embodiments, the sensor includes the enzyme/polymer layer and the hydrophobic layer disposed between the enzyme/polymer layer and the immobilized enzyme layer such that the enzyme/polymer layer is disposed along the hydrophobic layer within an area above the immobilized enzyme layer.

187 citations

Journal ArticleDOI
TL;DR: Gels formed by cross-linking functionalized poly(ethylene glycol) (PEG) and a lysine-containing polypeptide through the action of a natural tissue enzyme, transglutaminase hold potential for forming highly hydrated networks around living cells.
Abstract: We demonstrate formation of a hydrogel network by cross-linking functionalized poly(ethylene glycol) (PEG) and a lysine-containing polypeptide through the action of a natural tissue enzyme, transglutaminase. The enzyme reaction rate using a PEG-modified peptide substrate is the same as the reaction rate for free substrate. Both the ratio and total concentration of the two macromers determine whether gelation will occur and the nature of the gel which forms. Under suitable conditions, clear gels form and swell to give a final composition which is 90% water. Diffusion coefficients of small proteins and albumin in the gel are comparable to those in free solution. Gelation proceeds under mild conditions and thus these gels hold potential for forming highly hydrated networks around living cells.

186 citations

Journal ArticleDOI
TL;DR: In this article, a series of chemically modified lecithins were used to investigate by kinetic analyses their substrate c.q. inhibitor properties for porcine pancreatic phospholipase A.

186 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202214
2021807
20201,053
20191,064
20181,112
20171,024